Method of and apparatus for heat-treating metallic articles



H. P. MACDONALD. METHOD OF AND APPARATUS FOR HEAT TREATING METALLIC ARTICLES.

' APPLICATION FILED FEB. 4, I9I9.

Patented Apr. 6, 1920.

UNITED-STATES PATENT OFFICE.

HARRY 1?. MACDONALD, OF MONTCLAIR, NEW JERSEY, ASSIG-NOR TO THE SNEAD & C0. IRON WORKS, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

METHOD OF AND APPARATUS FOR HEAT-TREATING- METALLIC ARTICLES.

This invention relates to an wimprovedmethod of and apparatus for heat treating metallic articles, particularly tubing.

In general respects, the apparatus I employ in carrying out my invention is the same as that shown in United States Letters Patent to Macdonald and Huggins, No. 1,274,919. The apparatus shown in such patent comprises in the main, a vertical frame carrying an upper and a lower pair of contact jaws adapted to receive the tube to be treated, the tube being suspended in vertical position and being discharged, after heat treatment, into an oil or other quenching bath located at the foot of the frame.

I have found that it is frequently necessary to give each piece of tubing three different heats in order to obtain the desired properties in the finished tube. In the first heat the tube is brought to the point of decalescene and. is then quickly cooled or quenched. It is then again heated to the decalescent poin, cooled, and finally reheated to the drawing temperature and set aside to cool slowly.

It will be seen, therefore, that in the type of apparatus described, a considerable amount of additional work and a loss of time was entailed, owing to the fact that after the-first heat,'it was necessary to dischargee the tube into the bath, remove it from the bath, replace it in the machine,

where it was reheated and again discharged, to be again removed from the bath and replaced in the machine, and then, after reheating to the drawing temperature, setaside for cooling.

It is the purpose of my present invention to overcome the foregoing difiiculties and to provide an improved'method and apparatus whereby" the heat treating operations can be carried out expeditiously mum number of operations.

I accomplish the foregoing, together with such other objects as may hereinafter appear, by means of a construction which I' and with a miniand the quenching medium is discharged Specification of lietters Patent. Patented Apr. 6, 1920. Application filed February 4, 1919. Serial No. 274,922.

have illustrated in preferred form in theaccompanying drawings, wherein:

Figure 1 is a diagrammatic side elevation of the main supporting frame' with its tube supporting contacts, and with the means for quenching the tube, while in the machine, in position to be placed in operation; Fig. 2 is an enlarged section througha portion of the tube with the quenching means,

expand during the heating and cooling op.-

erations, the lower pair of jaws C being movable for this purpose by reason'of the fact that its holding bolts pass through elongated slots in the frame (see dotted lines Fig. 1). Current is passed through the tube by means of the leads 8 and 9, and the tube is heated by its internal resistance to the passage of the current. y

In treating the tube, the operator first turns on the current and heats the tube to the decalescent point, which he may determine in any one of a number of different ways, and when this point is. reached, the current is turned'iofl. Instead of then discharging the tube, in the manner shown in said patent, I leave the tube in the machine and lower into it a quenching-element 10 preferably in the form of a pipe, closed at the bottom and provided with a plurality of apertures 11v extending through the wall thereof. The pipe is supplied with oil,

11 is preferably lowered into the tube, .and-

'upon, or just previous to, introduction of the pipe into the tube, the valve 14 is opened through the apertures 11 in such manner as to impinge substantially uniformly upon the entire inner surface of-the tube.

After the tube has been quenched the pipe 11 is removed, current is again turned on, and the tube again'brought to the decalescent point, after which it is again quenched in the manner described, when the pipe 11 is withdrawn and the tube heated to the drawing temperature, whereupon it is removed from the machine and set asideto cool slowly. In some cases, it may not be necessary to give the second heat.

The modification shown in Fig. 3 is particularly adapted for use where the quenching medium is cold air, although this form of quenching apparatus may also be employed with other quenching mediums, It differs from the apparatus just described in that the pipe 11 is open only'at the bottom end where itis provided with a cone-like jet member 15, which is adapted to discharge the quenching medium in a laterally directed substantially uniform spray. With this construction; however, the valve 14 is opened just before or at the time theend of the pipe is introduced, and the pipe is lowered at a uniform speed. Depending upon the treatment desired, it may be necessary to raise and lower the pipe several times throughout the length of the tube before the valve is closed.

It will be seen from the foregoing that I have. provided an apparatus for applying the quenching medium internally and this is advantageous not only because it makes it unnecessary to remove the tube from the machine for the various operations, but also because the internal application of the quenching medium can be made more uniformly than an external application, and in addition, the quenching medium is more effective.

Furthermore, it will be seen that the quenching medium iscentirely under the control of the operator and the tube may be "cooled to any desired point necessary. This effects a saving in'current for the reason that the operator, after the tube has been quenched, and whileit is still hot, can switch on the current and start the reheating, whereas when the tube is dropped into an oil bath, it acquires the temperature of the bath and syfiicient current has to be used on the subsequent beatings to raise it from that temperature to the temperature desired for the treatment. The use of cold air for most advantageous I A taneously and uniformly heating all pora quenching medium isin this respect. I have found the foregoing process to be particularly valuable in the treatment of tubing such as referred to in the aforemen .tioned Letters'Patent in which the wall of the tube'is relatively thin. An example of such tubing specified. in. the said Letters Patent is a tube about ten feet long, an inch.

in diameter with a thickness of wall of aboutv one-sixteenth of an inch. It will be seen that with such material in which the thickness of the wall is relatively such that the heating and quenching are accomplished with great speed considerable difliculties are encountered in heat treatment, particularly with reference to the securing of the proper physical conditions throughout the metal.

I claim 1. The, herein described process of heat treatinggmetallic articles which consists in heating the, article in suitable supporting mechanism; and in quenching thearticle, in reheating the article before cooling, in quenching the article, and in reheating the article to drawing temperature, in situ.

2. The herein described process of heat treating metallic tubing, which consists in heating the tube in suitable supporting mechanism by passing an electric current therethrough; and in quenching, the tube in site; in again reheating the tube by passing the electric current therethrough before the tube has cooled; and in cooling the tube.

ing the tube in sz'tu at the eritical point;

and in again reheating the tube by passing thev current of electricity therethrough to a drawing temperature.

4. The herein described process of heat treating relatively thin tubing having a substantially uniform diameter and a substantially uniform thickness of wall which consists in simultaneously and uniformly heating all portions of the tube, and in simultaneously quenching the tube throughout its length by applying a quenching medium to the interior thereof substantially uniformly.

5. In the heat treatment of hollow metallic articles, the step which consists in simultaneously and uniformly heating all portions of the article by passing an electric current therethrough, and in uniformly applying a quenching medium in the interior of the article in situ.

6. In the heat treatment of hollow metals lic articles, the step which consists in. simultions of the article by passing .an electric current therethrough, and in substantially,

uniformlyv applying a gaseous quenching medium in the interior of the article in site.

In testimony whereof I have hereunto signed my name.

HARRY P. MACDONALD. 

